什么是PDF？
PDF（可移植文档格式）是由Adobe开发的一种文件格式，以独立于硬件、软件和操作系统的方式呈现包含文本、图像和格式的文档。
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What is it?
PDF（可移植文档格式）由Adobe于1993年创建，并于2008年成为开放标准。它以固定布局捕捉文档 - 包括文本、字体、矢量图形和图像 - 在任何设备或操作系统上看起来都相同。
PDF可以包含交互元素，如表单、超链接和数字签名。它们支持加密和密码保护，使其成为全球法律、金融和官方文档的标准。
Technical Specifications
Pros & Cons
Advantages
Opens identically on any device, OS, or screen size without font or layout changes.
Password protection, encryption, and digital signatures for sensitive documents.
Efficient compression keeps files small while preserving full quality.
The standard format for professional printing and publishing workflows.
Disadvantages
Editing PDF content requires specialized software - not as easy as Word documents.
Does not reflow text for different screen sizes like EPUB does.
PDFs with many images or embedded fonts can be significantly large.
Untagged PDFs can be difficult for screen readers and assistive technology.
When to Use It
当需要一致的格式和通用兼容性时，PDF是正确的选择。
Business Documents
Contracts, invoices, reports, and proposals that must look identical for all recipients.
Legal and Official
Court documents, government forms, and certificates require the fixed layout PDF provides.
Publishing
E-books, brochures, and magazines distributed digitally in a print-ready format.
Forms
Interactive PDF forms allow users to fill in and submit data while preserving the document structure.
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Our free online converter supports all major formats. No software to install, no registration required.
Start Converting NowFrequently Asked Questions
Can I edit a PDF file?
Yes, but you need PDF editing software. Adobe Acrobat is the most capable option. Free alternatives include LibreOffice Draw and various online PDF editors for simple changes.
Why is my PDF so large?
Large PDFs usually contain high-resolution images or embedded fonts. Use a PDF compressor to reduce the size - our tool can often reduce PDFs by 50-80% without visible quality loss.
How do I password protect a PDF?
Use a PDF editor or our online PDF protection tool to add password encryption. You can set separate passwords for opening and for editing/printing the document.
Is PDF the same as a scanned document?
Not always. A PDF can contain real text (searchable and copyable) or just an image of text (a scan). Scanned PDFs need OCR processing to make the text searchable.
What is PDF/A?
PDF/A is an ISO-standardized version of PDF designed for long-term archiving. It embeds all fonts and color profiles and prohibits features like encryption that could affect future readability.